High temperature alloy



Patented May 25, 1948 Lee E. Osman, Marblehezd, Mass, assignor to *General Electric Company, a corporation of New Xork .No :Drawing. Application May 2-3,, r1945, Serial No. 595,486

"4 "Claims. 1

The present invention is :an alloy adapted ifor use as a wheel material insupercharger-turbines and the like.

It is one of the objects of the invention to provide an alloy which develops suflicient strength from h'eat treatment without cold Working.

In carrying out the present invention I employ an alloy having a carbon content of 0.25 to 0.35%, about 16 to 18% chromium, about 12 to 14% nickel, about 1.75 to 2.25% molybdenum, about 0.8 to 1.2% tungsten, about 0.4 to 0.6% silicon, about 1.25 to 1.75% manganese, about 0.7 to 1.0% columbium, about 0.45% to 1.20% beryllium, with the balance iron. A preferred alloy composition consists of 0.30% carbon, 17% chromium, 13% nickel, 2% molybdenum, 1% tungsten, 0.5% silicon, 1.5% manganese, 0.8% columbium, and 1% beryllium with the balance iron.

The alloy may be forged at 2000-2100 F. to 1600-1700" F. In order to develop the optimum properties in the alloy, it is quenched from a temperature of about 1050 C. and thereafter aged for about 15 to 24 hours at 650C. The alloy as quenched has a Rockwell C hardness of 15 to 20. After aging at 650 C. the Rockwell C hardness is 40 and remains substantially constant at that figure. The alloy does not air harden.

The structure after solution treating and aging is duplex consisting of a mixture of alpha and gamma solid solutions together with the precipitated compounds and carbides. Precipitated compounds are believed to be complex iron and nickel beryllides. The ratio between the alpha and gamma solid solutions apparently depends on the composition, the nickel-chromium ratio having a decided effect in this respect and also the percentage of beryllium which restricts the gamma field of the iron-nickel-carbon alloys similar to chromium but to a greater extent.

The solution temperature of 1050 C. provides satisfactory results. If a higher solution temperature is employed, for example a solution temperature of about 1150 C. there appears to be a tendency to cause some grain boundary fusion of the beryllium which adversely affects the ductility and also the yield strength and rupture strength of the alloy. The lower solution temperature of 1050 C. avoids this difficulty and also provides material having a higher rupture strength.

Although the maximum hardness in the alloy is obtained with an aging temperatiu'e of 500 C., I generally employ an aging temperature of 650 C. since that is usually the maximum operating temperature of supercharger bucket wheels. Above 500 C. the hardness progressively decreases ;2 idl-thoug h mo considerable decrease is sound lup to W C. :I-Iowever, rat 800 '0. a substantial:'so'ftening takes place.

Tensile and rupture properties at room temperature of my preferred alloy composition in the form of forged bars which have been heated at 1050 C. for one hour, water quenched and aged at 650 C. for hours and then air cooled, are as follows: l0

Approx- Tensile Results imate Proportional Limit Tensile Tested at Strength Bars Elong. Red. Area Room Temp. 1000 F Rupture results at 1200 F.

Elongation,

Stress,

Per Cent 25 I Hours per sq. in.

Although I prefer to employ an alloy which contains columbium. and both molybdenum and tungsten I have employed alloys having approximately the following compositions in which either the columbium or both columbium and tungsten have been omitted:

Given substantially the same heat treatment as Letters Patent of the United States, is:

1. A heat treated iron base alloy containing about 0.25 to 0.4% carbon, about 16 to 18% chro- I mium, about .12't0 14% nickeL-about 2 to 4.5% metal from the group'consisting -of tungsten-and molybdenum, about 0.4 to 1% silicon, about 1 to 1.75% manganese, about 0.45 to 1.2% beryllium with the balance substantially. all iron.

2. A heat treatable iron base alloy containing about 0.25 to 0.35% carbon," about 16 to 13% 1 chromium, about 12 to 14% nickel, about 1.75to

2.25% molybdenum, about 0.8 to 1.2% tungsten,

about 0.4 to 0.6% 'silicon about' 1.25 to 1.75% manganese, about 0.45 to 1.2% beryllium with the balance substantially all-iron. 7

3. A heat treatable iron base alloy containing about 0.3% carbon, about 17% chromium, about 13% nickel, about 2% molybdenum, about/1% tungsten, about 0.5% silicon, about 1.5manganese, about 1.0% beryllium with the balance substantially all iron. r

4. A heat treatable iron base alloy containing about .19 to .43% carbon, about 14.9 to 18% chromium, about 11.4 to 15% nickel, .90 to 5.51% ofgmetal from the group consisting, of .tungsten 'fanjd'. molybdenum, about .4 to 1.23% silicon, about x 1.1 to 1.75% manganese, about .45 to 1.2% beryl- 10 lium with the balance substantially all iron..

)7 LEE E. OSMAN.

-REFERENCES CI D V The-following references areof record inthe l5 ille of this patent: V

-UNITED STATES PATENTS Number 7 Name 7 Date 7 2,125,929 Krivobok ,2 Aug, 9, 1938 20 2,161,926 fJonas ..'...1 June 15, 1939 2,240,064 Allen et a1 Apr. 29, 1941 2,373,490 Mohling Apr; 10, 19.45 

